Test your knowledge: Real-World Patterns

Question 1 of 6

The robust pageview pattern sends the ping…

The lesson's flusher exists precisely because two signals can both arrive.

Answer options A on DOMContentLoaded, before the user can navigate away B on the FIRST of visibilitychange → hidden or pagehide, debounced C on beforeunload, which fires before any teardown D every 30 seconds as a heartbeat

Racing visibilitychange → hidden against pagehide and debouncing gives one ping per view on every platform — including mobile kills that never reach pagehide, and bfcache restores that arrive via pageshow instead.

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Question 2 of 6

The JSON error-reporting pattern sends `Content-Type`-safe JSON by…

A JSON-typed Blob flips cross-origin sends into preflight mode — a collector without CORS answers drops them silently.

Answer options A setting Content-Type: application/json through a Blob B sending the JSON as a text/plain string and parsing server-side C URL-encoding the JSON into the query string D base64-encoding the payload into a FormData field

An application/json Blob is not CORS-safelisted: the request flips into cors mode and a preflight follows — a cross-origin collector without CORS setup drops it silently. The text/plain string rides no-cors with no preflight; the collector reads the body and JSON.parse()s it — errors report themselves without generating new ones.

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Question 3 of 6

Crash reporting with beacons must solve the ordering problem:…

A hard crash leaves no in-flight guarantees — so the report outlives the page.

Answer options A the crash payload must be the LAST request before process death B queued crash reports need persisted state, because the NEXT page load does the sending C beacons cannot carry stack traces D the SW must originate the crash beacon

The pattern persists crash payloads (localStorage/IndexedDB) with a 'send on next load' flag: the dying page queues the report beacon best-effort, and the next session's startup drains the queue — belt and suspenders.

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Question 4 of 6

Correct bfcache analytics distinguishes restores from new pageviews by…

The persisted flag on pageshow is the restore signal the spec gives you.

Answer options A ignoring pageshow entirely B listening for pageshow with persisted: true and shipping a restore-tagged pageview C checking performance.navigation.type D comparing session storage across loads

pageshow.persisted === true marks a bfcache restore. The pattern ships a fresh pageview tagged navigation_type: 'bfcache_restore' — so restored sessions count without inflating new-visit metrics. notRestoredReasons (when available) explains why restores fail.

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Question 5 of 6

Why does A/B test assignment need beacon-safe persistence?

A lost assignment flips the user into a different arm — measurement corruption, not a lost ping.

Answer options A Assignments must survive the page's death AND arrive even when death races the send B localStorage is blocked in private mode everywhere C Beacons cannot read cookies synchronously D The quota rejects tiny assignment payloads

The pattern writes the assignment to storage FIRST, then best-effort-beacons it, and reconciles server-side by client id: whichever arrives — the storage echo on the next load or the beacon now — the arm stays sticky.

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Question 6 of 6

The `analytics-sdk.js` reference recipe integrates the earlier patterns as…

It is the analytics SDK — every client-side recipe in the series, composed.

Answer options A a server-side pipeline for beacon payloads B the client SDK layer: lifecycle flusher + quota queue + safe payloads + transport choice in one entry point C a tag-manager loader for third-party beacons D a dashboard for beacon delivery rates

The SDK exposes track()/flush() over the lifecycle flusher (right moment), the CORS-safe builder (right payload), the quota queue (right budget), and the hybrid transport (right API per moment) — the whole series in one importable module.

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Test your knowledge: Real-World Patterns